1. Field of the Invention
The present invention relates generally to magnetic shields and magnetic poles for read heads and write heads of magnetic sensors, and more particularly to laminated, nitrided iron, nickel-iron magnetic shields and magnetic poles having a composition gradient.
2. Description of the Prior Art
As is well known to those skilled in the art, the fabrication of magnetic sensors having read head elements and write head elements involves the deposition and shaping of a plurality of thin film layers of various materials utilizing photolithographic, etching and other process steps. The read head elements and write head elements are fabricated on the surface of a substrate base, and after fabrication, the substrate is sliced in such a manner as to create the magnetic sensors. In a typical prior art fabrication process, read head elements and write head elements may be fabricated adjacent to each other and aligned so as to create a linear sensor element of a tape drive head when the fabrication process is complete, or the read head elements and write head elements may be fabricated one on top of the other to form a magnetic head of a hard disk drive.
The focus of the present invention is upon the fabrication and composition of the magnetic shields of the read head element and the magnetic poles of the write head elements, and the present invention relates to improvements in the process for fabricating the shield or pole components.
Regarding the magnetic shield layer, it is known in the prior art that where the layer is composed of Permalloy that it will have superior magnetic shielding properties, however this material is quite ductile and metal bridging problems are known to occur during head polishing and with wear from usage that can result in electrical shorting by the Permalloy across an insulation layer to the MR sensor elements. It is likewise known in the prior art that where the magnetic shield layer is composed of Fe, that a harder, less ductile layer results in which bridging and electrical shorting is not a problem. However, an Fe shield is less magnetically stable than a Permalloy shield, and additionally, an Fe shield is susceptible to corrosion and degraded performance where a Permalloy shield is not. A prior art shield that resolves some of these problems involves the fabrication of a laminated shield, in which alternating thin film layers of Permalloy and Fe are sequentially deposited. Additionally, to further improve the properties of the prior art laminated shield, the layers are nitrided as they are deposited. A specific laminated, nitrided shield layer of the prior art includes an Fe(N) 600 Å, NiFe(N) 200 Å laminated layer, which this two sublayer lamination is repeated a plurality of times to create the shield layer. As is described hereinbelow, the present invention involves an improvement in such laminated layers, in which a composition gradient is employed, such that the laminated layer structure provides superior magnetic shield properties at the read head element location and superior P1 magnetic pole properties at the write head element location.